1. Field of the Invention
The present invention relates generally to architectures for service provider networks, and more particularly, to novel architectures for evolving traditional service provider networks and methods to optimize traditional service provider networks, as well as, the disclosed novel architectures.
2. Description of Related Art
As is known in the art, a traditional service provider network includes a plurality of processing sites generally referred to as stations or nodes connected by one or more physical and/or logical connections. When the connections establish transmission of a signal in one direction between the nodes, the connections are generally referred to as links. Each node typically performs a switching function and one or more additional functions. The nodes may be coupled together in a variety of different network structures typically referred to as network topologies. For example, network nodes may be coupled in a circular structure, generally referred to as a ring topology. Other topologies such as star topologies and tree topologies are also known.
The transmission of a signal from a first or source node to a second or destination node may involve the transmission of the signal through a plurality of intermediate links and nodes coupled between the source node and the destination node. Such a succession of links and nodes between a source node and a destination node is referred to as a path. When a link or node in a path fails, communication between a source node and a destination node in that path is disrupted. Thus, to continue communications between the source and destination nodes, an alternate path must be found and the signal being transmitted from the source node to the destination is routed through the alternate path.
A self-healing network refers to a network that automatically restores connections among nodes in the event of a link or node failure in a path from a source node to a destination node. There is a growing trend and reliance on such networks owing to increasing reliance on and use of high-speed communication networks and the requirement that these communication networks be robust in the case of certain failures. Self-healing networks typically detect and report a failure, establish and connect a restoration path and then return the network to normal communications. Such self-healing characteristics are incorporated, for example, in the Synchronous Optical Network (SONET) protocols.
Generally, a Synchronous Optical Network (SONET) is both a standard and a set of specifications for building high speed, digital communications networks that run over fiber-optic cables while interfacing with existing electrical protocols and asynchronous transmission equipment. The use of fiber-optics in such networks provides a dramatic increase in available bandwidth (currently estimated in the hundreds of gigabits per second). One of the principal benefits of SONET is that it allows for the direct multiplexing of current network services, such as DS1, DS1C, DS2, and-DS3 into the synchronous payload of Synchronous Transport Signals (STS). The STS provide an electrical interface that is used as a multiplexing mechanism within SONET Network Elements (NE). In the SONET multiplexing format, the basic signal transmission rate, i.e., STS-1, operates at 51.84 million bits per second. AN STS-1 can carry 28 DS1 signals or one asynchronous DS3. STS-1 signals are then multiplexed to produce higher bit rates STS-2, STS-3, etc. This sometimes referred to as grooming. SONET signal levels are also defined in terms of an optical carrier (OC). Since the bit rates are the same in each case, the bit rate of the STS-1 equals the bit rate of the OC-1 with the only difference relating to the type of signal that is being referenced. For example, if the signal is in an electrical format, it is referred to as an STS. Similarly, if the signal is in an optical format compatible with a fiber medium, the signal is referred to as an OC.
SONET uses time division multiplexing (TDM) wherein multiple channels are given different time slots within a frame. Each node in a SONET based network includes an add-drop multiplexer (ADM) that interfaces the fibers to the electronic devices that are to communicate with each other over the network. A SONET network provides reliable transport from point to point and has the capability of providing “restoration.” The SONET ADM provides two broad functions. The first function is extracting information in one of the time slots from the incoming working fibers and outputting information into that time slot for transmission (along with the information in the other time slots) on the fiber that continues in the same direction. The second function is performing electrical switching to reroute information onto the protection fibers in the event of a failure in one or more of the fiber links.
One of the most common ways in SONET to “restore” network functionality rapidly is to combine Self Healing Rings (SHRs) and diversity protection (DP), using add-drop multiplexers (ADMs), for automatic protection switching. Systems using One-to-n (1:n) DP have one protected fiber for n working fibers. SHR architectures may be classified into unidirectional rings, in which the duplex channel travels over a different path than the forward channel, and bi-directional line switched rings (BLSRs) where the forward channel and the duplex channel travel the same path. Bi-directional line switched rings (BLSRs) typically include two or four fibers. Using ADMs, the restoration time is typically about 50 milliseconds (ms) for BLSRs utilizing SONET protocols while path switching typically requires less than 20 ms and loopback switching typically require under 80 ms.
Traditional service provider networks typically own and operate multiple overlay SONET-based BLSR networks. FIG. 1 is a diagram illustrating an example of a typical network architecture 100 representing the existing overlay networks of a traditional service provider network. An exemplary node (e.g. a core node or a transport node) is shown in FIG. 1. An access layer 102 (below the line 103) provides various services to the network and a transport layer 120 connects together the nodes of the network. In this example the services provided are: Time Division Multiplexing (TDM) voice (domestic and international) and private lines (PL) 104, voice-over IP (VoIP), Asynchronous Transfer Mode (ATM) and Frame Relay (FR) 106, Internet Protocol (IP) 108-dial-up or virtual private network (VPN), and leased λ service 109 (e.g. OC-48 rate). The private lines are supported through appropriate grooming at the transport layer 120. Similarly, the leased λ service is provided and restored through an optical switch 128 having both working and protected (W and P) lines. At the transport layer 120 (above the line 103), typical service providers sometimes utilize a bi-directional line-switched ring (BLSR) network architecture 124 that utilizes the SONET protocols previously discussed. The BLSR architecture 124 includes both working and protected (W and P) lines. Unfortunately, for each service the traditional service provider network provides (e.g. Voice, IP, ATM), the traditional service provider must operate a separate overlay network, thus utilizing multiple overlay BLSR networks, which becomes very costly.
Although these types of network architectures used by traditional service providers are capable of supporting most existing services, as IP-based services and traffic grow, a more cost effective network architecture is needed. The cost associated with building and operating multiple overlay networks has become an impeding factor for traditional service providers to stay competitive.